Poly-(-2-aminoalkyl)polyamines

ABSTRACT

Poly-(-2-aminoalkyl)polyamine compounds are provided having the following formula:   &lt;IMAGE&gt;   wherein: n is an integer of from 3 to about 12; R1 is selected from H and an alkyl group containing from 1 to about 10 carbon atoms; R2 and R3 are each independently selected from H and a lower alkyl group containing from 1 to about 6 carbon atoms; R4 is selected from H and   &lt;IMAGE&gt;   and R5 is selected from an alkyl group containing from about 6 to about 25 carbon atoms.

The present invention relates to poly-(-2-aminoalkyl)polyaminecompounds, and to methods for curing epoxy resins whereinpoly-(-2-aminoalkyl)polyamine compounds are employed as a curing agent.The present invention also relates to epoxy resin compositionscontaining poly-(-2-aminoalkyl)polyamine compounds as epoxy curingagents.

Epoxy resins were first introduced commercially in the United States inabout 1950 and since then their use has grown rapidly. Epoxy resins maybe broadly defined as resinous intermediate materials which arecharacterized by the presence of the epoxy group ##STR3##

In general, epoxy resins are not used by themselves but rather theyrequire the addition of a curing agent or hardener to convert them intoa thermoset material. Epoxy resins have gained wide acceptance instructural applications and in protective coatings because of theirgenerally excellent toughness, adhesion, chemical resistance, andelectrical properties. The combination of these properties is generallynot found in any other single plastic material.

A relatively large number of chemical reagents are available or known tohave utility as curing agents or hardeners which may be added to epoxyresins to convert them to thermoset materials. It is also known that thecuring process both the epoxy and the hydroxyl groups of the resin maybe involved. Curing agents are available whereby curing may beaccomplished at room temperature or upon heating. Curing may take placein general either by a coupling or addition process, or by catalyticpolymerization.

The known curing agents or hardeners for epoxy resins fall into threecategories: (1) the acidic type, e.g., acid anhydrides; (2) aldehydecondensation products, e.g., phenol-, urea-, and melamine-formaldehyderesins; and (3) amine type, e.g., aliphatic and aromatic amines,polyamides, tertiary amines, and amine adducts. The novelpoly-(2-aminoalkyl)polyamine compounds of the present invention may beemployed as the third type, namely the amine type, of epoxy curingagent.

The poly-(-2-aminoalkyl)polyamine comounds of the present invention maybe represented by the following structural formula: ##STR4## wherein:

n is an integer of from 3 to about 12;

R₁ is selected from H and an alkyl group containing from 1 to about 10carbon atoms;

R₂ and R₃ are each independently selected from H and a lower alkyl groupcontaining from 1 to about 6 carbon atoms;

R₄ is selected from H and ##STR5## and

R₅ is selected from an alkyl group containing from about 6 to about 25carbon atoms.

The present invention also relates to the use of such compounds as epoxycuring agents and to epoxy resin compositions which contain 100 parts byweight of at least one epoxy resin and from about 15 parts to about 50parts, preferably about 20 parts to about 30 parts by weight, of thepoly-(2-aminoalkyl)polyamine compounds of the invention. Such curedproducts have good flexiblity, high heat distortion temperatures, andexcellent solvent resistance.

The compounds of the present inventions may be conveniently prepared ina two-step process. In a first step, an intermediate,poly-(-2-nitroalkyl)polyamine, may be prepared by a condensationreaction of the nitroparaffin with an aldehyde such as formaldehyde anda suitable polyamine according to the following generalized reaction:##STR6## where R₁, R₂, R₃, R₄, R₅, and n have the values given above.

The nitroparaffin employed as a starting material preferably may be acompound of the formula ##STR7## wherein R₂ is H or aliphatic groupscontaining from about 1 to about 9 carbon atoms.

Some commonly available useful nitroparaffins are nitromethane,nitroethane, 1-nitropropane, 2-nitropropane, and high-ordernitroparaffins containing up to about 10 carbon atoms. Particularly goodresults may be obtained using 2-nitropropane, which is preferred.

The polyamines which may be employed as a starting material in the abovereaction may be selected from a wide range of compounds, although apreferred class of such compounds is those having the general structure

    R.sub.5 --NH.sub.2

wherein R₅ has the value set forth above. A particularly usefulpolyamine is one having the formula ##STR8## where x and y areindependently selected from integers of from 1 to about 6, preferably 2to 5. Most preferably x is 3 and y is 4.

According to an alternative embodiment, rather than preparing thepoly-(-2-nitroalkyl)polyamine by the above-described in situ reaction ofthe nitroparaffin, aldehyde, and polyamine, thepoly-(2-nitroalkyl)polyamines may be prepared in a two-step process byfirst reacting the aldehyde with the nitroparaffin and then reacting thecorresponding nitroalcohol with the polyamine in a separate reactionaccording to the following sequence: ##STR9## where R₁, R₂, R₃, R₄, R₅,and n have the values set forth above.

The reaction of nitro-paraffin, formaldehyde, and polyamine may becarried out at a temperature of from about 20° C. to the boiling pointof the mixture. The preferred temperature is from about 75° C. to about120° C. The use of a solvent is not critical in the preparation ofpoly-(2-nitroalkyl)polyamines; however, the use of a mutual solventprovides a homogeneity for all the reactants and facilitates mixing.Lower alcohols, such as methyl alcohol, ethyl alchol, and isopropylalcohol, are preferred. At least stoichiometric amounts of2-nitropropane, aldehyde, and polyamine may be used. Excess aldehyde andpolyamine may be used without adverse effects.

The preferred molar ratio is about an equivalent number of moles ofnitroparaffin and aldehyde which is equal to the number of primary aminonitrogens in the polyamine or the preferred moles of nitroalcohol usedis equal to the number of primary amine nitrogens in the polyamine.

The crude poly-(2-nitroalkyl)polyamine may then be isolated by anyconvenient means as, for instance, by solvent extraction and may then bereduced to the poly-(-2-aminoalkyl)-polyamine compound with hydrogen anda suitable metal catalyst according to the following equation: ##STR10##wherein R₁, R₂, R₃, R₄, R₅, and n are defined above.

The poly-(-2-aminoalkyl)polyamine(s) were prepared by passing hydrogenthrough a catalyst-containing solution of poly-(-2-nitroalkyl)polyaminein suitable solvent. Solvents include lower weight alcohols such asmethyl alcohol, ethyl alcohol, and isopropyl alcohol; ethers such asdioxane; hydrocarbons such as benzene, toluene, xylenes, cyclohexane,and petroleum ether; and mixtures of lower weight alcohols and watersuch as about equal parts by weight of ethyl alcohol and water. Theamount of solvent is not critical. The preferred solvent is methylalcohol in an amount of about 30 percent to about 80 percent by weight.

Any suitable reduction catalyst may be used to catalyze the reduction ofthe poly-(-2-nitroalkyl)polyamine to the poly-(-2-aminoalkyl)polyaminecompound. Catalysts such as Raney nickel; nickel oxides; finely dividedmetals such as iron, cobalt, platinum, ruthenium, osmium, and rhodiummay be used. Furthermore, metal catalysts supported on pumice, asbestos,kieselkuhr, alumina, silica gel, or charcoal work equally as well. Theamount of catalysts used depends on such reaction variables astemperature, pressure, and time, and it can vary from about 0.025percent to about 15 percent by weight of thepoly-(-2-nitroalkyl)polyaine. The preferred catalyst is Raney nickel orsupported nickel present from about 0.1 percent to about 15 percent byweight of the poly-(-2-nitroalkyl)polyamine. Thepoly-(-2-nitroalkyl)polyamine may be reduced at a temperature of fromabout 20° C. to about 120° C., although temperatures of from about 40°C. to about 75° C. may be preferred since they may provide fasterreaction times and higher yields of poly-(-2-aminoalkyl)polyamines.During the reduction of poly-(-2-nitroalkyl)polyamine, pressures rangingfrom about 100 to 3,000 psi, preferably from about 500 to 1,500 psi, ofhydrogen may be used.

The process of reducing the poly-(-2-nitroalkyl)polyamines has beendescribed as a batch operation carried out in a high-pressure stirredautoclave; however, other reducing modes may give equally good results.A continuous flow reactor may be used with suspended- or fixed-bed solidcatalysts operating at the proper temperature, pressure, and flowrate togive the desired reduction. Most preferably, the desired reduction maybe accomplished by incremental addition of thepoly-(-2-nitroalkyl)polyamine to a batch-type reactor at the properdescribed operating conditions.

Substantially pure, low molecular weight polyamines can be separatedfrom the reaction mixture by filtration of the catalyst and insolublematerial, distilling off the solvent and thereafter distilling theresidue under reduced pressure. Where higher molecular weight polyaminesare prepared and where mixtures of non-stoichiometric reaction ratioswere used, the resulting products may be more difficult to purify.Therefore, these products may generally be used as obtained without anyadverse effects. Reaction product(s) were characterized by GC-massspectra, IR, proton NMR, Carbon-13 NMR, and elemental analysis.

One particularly important use for the novel compounds of the presentinvention is their use as epoxy curing agents for polyepoxides. Thepolyepoxides which can be cured at elevated temperatures using the aminocompounds as herein described are those polyepoxides possessing at leasttwo ##STR11## groups. These groups may be terminal, i.e., ##STR12##groups, or they may be in an internal position; however, especiallydesirable results can be obtained when the epoxy groups are terminal.The polyepoxides may be saturated or unsaturated, aliphatic,cycloaliphatic, aromatic, or heterocyclic, and may be substituted suchas with hydroxyl groups, ether radicals, and the like. Further, thepolyepoxides can be monomeric or polymeric. Such polyepoxides, and theirpreparation, are well known in the art.

The curing of the polyepoxides with the above-described polyamine curingagents of the present invention may be accomplished by simply mixing thetwo components together. While the reaction between the two componentsmay occur slowly at room temperature, improved results can be obtainedif the mixture is heated to a temperature of from about 50° C. to about180° C. for a period of time of from about 1 to about 12 hours andthereafter post-curing the reaction product for an additional period oftime from about 1 to about 8 hours at a temperature of from about 140°C. to about 225° C. With a small casting, curing the reaction mixturecan be obtained by heating the reaction mixture for about 2 hours at atemperature of from about 80° C. to about 100° C. and thereafterpost-curing the reaction product at a temperature of from about 140° C.to about 225° C. for an additional 2 hours or so.

In curing polyepoxides, it is generally desirable that the polyepoxidebe in a mobile condition when the curing agent is added to ensureuniform mixing. If the polyepoxide is extremely viscous or solid at roomor casting temperature, the polyepoxide may be heated to reduce theviscosity or a volatile liquid solvent which can escape from thepolyepoxide composition containing the novel polyamine curing agent byevaporation before and/or during the curing of such polyepoxidecomposition can be added to the polyepoxide to reduce its viscosity.Typical of such volatile liquid solvents are ketones, such as acetone,methyl ethyl ketone, and the like; ethers, such as ethyl acetate, butylacetate, and the like; ether alcohols, such as methyl, ethyl, or butylethers of ethylene glycol; and chlorinated hydrocarbons, such aschloroform.

In addition to the use of the polyamine compounds of the presentinvention as epoxy curing agents, many other uses can readily beenvisioned by those skilled in the art. Thus, not only do the compoundsof the present invention find utility as epoxy curing agents but suchcompositions can be employed as oil and fuel adductive intermediates.Further, the polyamimes may be employed for the formation ofdiisocyanate compositions for the incorporation into polyurethanecompositions, and the compound may be further reacted to form novel anduseful polyamides.

In order to more fully describe the preparation and use of the novelcompounds of the present invention, the following examples are given;however, such examples are presented for illustration only and are notto be construed as unduly limiting the scope of the present invention.Unless otherwise indicated, all parts and/or percentages given in theseexamples are by weight.

EXAMPLE 1

In a 1,000 cc three-necked flask equipped with a magnetic stir bar,thermometer, dropping funnel, reflux condenser with a Dean-Starkcollector, and heating mantle were placed115.3 gm (0.97 mole) of2-nitro-2-methyl-1-propanol, 150 ml of toluene, 10 cc of 2-nitropropane,and 167.8 g (0.97 mole) of 4-aminomethyl-1,8-octanediamine. This mixturewas then heated to reflux and 17.5 ml of water distilled over n theDean-Stark trap during the course of several hours. The reaction mixturewas allowed to relux until no water distilled over, indicating thatreaction was complete. On cooling, the toluene and unereacted startingmaterials were then distilled away from the product under vacuum (15-20mm Hg) to give a viscous pale orange product. A yield of 268.2 g, or100% of the crudepoly-(-2-nitro-2-methylpropyl)-4-aminomethyl-1,8-octane diamine wasobtained. An IR spectrum of the product indicated that nitro groups werepresent. The product was used without further purification.

EXAMPLE 2

In a 1,000 cc three-necked flask equipped with a magnetic stir bar,thermometer, dropping funnel, reflux condenser with a Dean-Starkcollector, and heating mantle were placed 238.8 (2 moles) of2-nitro-2-methyl-1-propanol, 250 ml of toluene, 20 cc of 2-nitropropane,and 173.3 g (1.0 mole) of 4-aminomethyl-1,8-octanediamine. This mixturewas then heated to reflux and 38 ml of water distilled over in the DeanStark trap during the course of three hours. The reaction mixture wasallowed to reflux until no water distilled over, indicating that thereaction was complete. On cooling, the toluene and unreacted startingmaterials were then distilled away from the product under vacuum (15-20mg) to give a viscous pale orange product. A yield of 378.6 gm, or 100%of the poly-(-2-nitro-2-methylpropyl)-4-aminomethyl-1,4-octanediamine,was obtained. An IR spectrum of product indicated that nitro groups werepresent. The product was used without further purification.

EXAMPLE 3

In a 2,000 cc three-necked flask equipped with a magnetic stir bar,thermometer, Dean-Stark trap collector, and heating mantle were placed357.3 g (3 moles) of 2-nitro-2-methyl-1-propanol, 250 ml of toluene, 20cc of 2-nitropropane, and 173.3 g (1 mole) of4-aminomethyl-1,8-octane-diamine. This mixture was then heated to refluxand 54 ml of water distilled over in the Dean-Stark trap during thecourse of several hours. The reaction mixture was allowed to reflux withno water distilling over, indicating that the reaction was complete. Oncooling, the toluene and unreacted starting materials were thendistilled away from the product under vacuum (15-20 mm Hg) to give aviscous pale orange product. A yield of 500.1 gm, or 100% of the crudepoly-(-2-nitro-2-methylpropyl)-4-aminomethyl-1,8-octanediamine, wasobtained. An IR spectrum of the product indicated that nitro groups werepresent. The product was used without any further purification.

EXAMPLE 4

In a 2,000 cc three-necked flask equipped with a mechanical stirrer,thermometer, Dean-Stark trap collector, and heating mantle were placed174 gm (6 moles) of 2-nitro-2-methyl-1-propanol, 1,000 cc of toluene,and 173.3 g (1 mole) of 4-aminomethyl-1,8-octanediamine. This mixturewas then heated to reflux and 104 ml of water distilled over in theDean-Stark trap during the course of several hours. The reaction mixturewas allowed to reflux until no water distilled over, indicating that thereaction was complete. On cooling, the toluene and unreacted startingmaterials were then distilled away from the product under vacuum (15-20mm Hg) to give a dark brown very viscous product. A yield of 714.4 gm,or 91.7%, of the crudepoly-(-2-nitro-2-methylpropyl)-4-aminomethyl-1,8-octanediamine wasobtained. An IR spectrum of the product indicated that nitro groups werepresent. The product was used without further purification.

EXAMPLE 5

In a 2,000 cc stirred autoclave were charged 148 gm of crudepoly-(-2-nitro-2-methylpropyl)polyamine from Example 2, 200 cc of methylalcohol, and 7.0 gm of Raney nickel catalyst. The autoclave was sealedand pressured with hydrogen gas. The reduction of thepoly-(-2-nitro-2-methylpropyl)polyamine was conducted at 40°-100° C. and1,000-1,600 psi hydrogen pressure until the hydrogen absorption wascomplete. On cooling, the reaction mixture was filtered from thecatalyst and the methyl alcohol and any volatiles were removed undervacuum to give a pale yellow liquid product. An IR spectrum of theproduct indicated that all the nitro groups had been reduced. The crudeproduct was further fractioned at 5.5 mm Hg (200°-230° C.) to givecolorless liquids of varying 2-amino-2-methylpropyl substitution, withthe major components being the di- and trisubstituted products.

EXAMPLE 6

In a 2,000 cc stirred autoclave were charged 150 gm of crudepoly-(-2-nitro-2-methylpropyl)polyamine from Example 3, 200 cc of methylalcohol, and 7.0 gm of Raney nickel catalyst. The autoclave was sealedand pressured with hydrogen gas. The reduction of thepoly-(-2-nitro-2-methylpropyl)polyamine was conducted at 40°-100° C. and1,000-1,600 psi hydrogen pressure until the hydrogen absorption wascomplete. On cooling, the reaction mixture was filtered from thecatalyst and the methyl alcohol and any volatiles were removed undervacuum to give a pale yellow liquid product. An IR spectrum of theproduct indicated that all the nitro groups bad been reduced. The crudeproduct was further fractionated at 160°-200° C. and 5.0-5.5 mm Hg togive colorless liquids of varying 2-amino-2-methylpropyl substitution,with the major component being the trisubstituted product.

EXAMPLE 7

In a 2,000 cc stirred autoclave were charged 150 gm of crudepoly-(-2-nitro-2-methylpropyl)polyamine of Example 1, 200 cc of methylalcohol, and 7.0 gm of Raney nickel catalyst. The autoclave was sealedand pressured with hydrogen gas. The reduction of thepoly-(-2-nitro-2-methylpropyl)polyamine was conducted at 40°-100° C. and900-1,500 psi of hydrogen pressure until the hydrogen absorption wascomplete. On cooling, the reaction mixture was filtered from thecatalyst and the methyl alcohol and any volatiles were removed undervacuum to give a colorless liquid. An IR spectrum of the productindicated that all the nitro groups had been reduced. This product wasused without further purification.

EXAMPLE 8

To 4 beakers, each containing 100 parts of epoxy resin based ondiglycidyl ether of bisphenol A (n=0.2, WPE=185-195), having theformula: ##STR13## were added the corresponding parts of4-aminomethyl-1,8-octanediamine: 14.0 parts, 15.0 parts, 16.0 parts, and17.0 parts. After mixing each beaker thoroughly for 2 minutes andcentrifuging at a speed of 3,000 rpm, these resin mixtures were placedin an aluminum mold and were cured for 2 hours at 80° C. and for another2 hours at 150° C. The crosslinked products had glass transitiontemperatures measured with a differential scannng calorimeter (PerkinElmer Model DSC-2) as are summarized in the Table below.

                  TABLE 1                                                         ______________________________________                                        GLASS TRANSITION TEMPERATURE FOR                                              4-AMINOMETHYL-1,8-OCTANEDIAMINE                                               ENTRY           PHR    Tg (°C.)                                        ______________________________________                                        1               14.0   138.6                                                  2               15.0   145.1                                                  3               16.0   140.1                                                  4               17.0   128.1                                                  ______________________________________                                    

EXAMPLE 9

A 5 PHR study was done with fractionatedpoly-(-2-amino-2-methylpropyl)polyamines from both Examples 5 and 6 withdiglycidyl ether of bisphenol A (n=0.2, WPE=185-195). After mixing eachsample thoroughly for 2 minutes and centrifuging at a speed of 3,000rpm, these resin mixtures were placed in an aluminum mold and wee curedfor 2 hours at 80° C. The crosslinked products had maximum glasstransition temperatures measured with a differential scanningcalorimeter (Perkin Elmer Model DSC-2) as are summarized in Table 2below. The percent weight (by GLC) of mono-, di-, and tri-substituted2-amino-2-methylpropyl is also included, as well as the4-amino-methyl-1,8-octanediamine starting material for comparison.

                  TABLE 2                                                         ______________________________________                                        GLASS TRANSITION TEMPERATURE FOR                                              POLYAMINE CURING AGENTS                                                       EN-  CURING             %      %    %                                         TRY  AGENT       PHR    MONO   DI   TRI  Tg (°C.)                      ______________________________________                                        1    4-aminomethyl-                                                                            17.0   --     --   --   145.1                                     octanediamine                                                            2    Example 5   21.0   20.0   60.0 20.0 151.3                                3    Example 6   23.0   10.0   24.0 66.0 156.6                                ______________________________________                                    

The above examples clearly show the preparation of the novel compound(s)of the present invention. Furthermore, Examples 8 and 9 demonstrate theuse of poly-(-2-aminoalkyl)polyamines as epoxy curing agents. Inaddition to the prolonged pot life observed for these novelpoly-(-2-aminoalkyl)polyamines, enhanced thermal properties were alsoobserved over the corresponding aliphatic counterparts. Table 2, Entry 3clearly shows a glass transition temperature about 12° C. higher for thepoly-(-2-aminoalkyl)polyamine.

What is claimed is:
 1. Poly-(-2'-aminoalkyl)polyamine compounds of theformula: ##STR14## wherein: n is an integer of from 3 to about 12;R₁ isselected from H and an alkyl group containing from 1 to about 10 carbonatoms; R₂ and R₃ are each independently selected from H and a loweralkyl group containing from 1 to about 6 carbon atoms; R₄ is selectedfrom H and ##STR15## and R₅ is an alkyl group containing from about 6 toabout 25 carbon atoms.
 2. The polyamines of claim 1, wherein R₂ and R₃are CH₃.
 3. The polyamines of claim 2, wherein R₁ is H.
 4. Thepolyamines of claim 3, wherein R₄ is H.
 5. The polyamine compounds ofclaim 1 where said alkyl group of said R₅ moiety is derived from anamine compound of the formula: ##STR16## where x and y are independentlyselected from integers of from 1 to about 6, wherein the functionalityof said compounds is provided by the reaction of at least one of theprimary amine groups thereof.
 6. Poly-(-2-nitroalkyl)polyamine compoundsof the formula ##STR17## wherein: n is an integer of from 3 to about12;R₁ is selected from H and an alkyl group containing from 1 to about10 carbon atoms; R₂ and R₃ are each independently selected from H and alower alkyl group containing from 1 to about 6 carbon atoms; R₄ isselected from H and ##STR18## and R₅ is selected from an alkyl groupcontaining from about 6 to about 25 carbon atoms.
 7. The compounds ofclaim 6, wherein R₂ and R₃ are CH₃.
 8. The compounds of claim 7, whereinR₄ is H.
 9. The compounds of claim 6, wherein said alkyl group of saidR₅ moiety is derived from an amine compound of the formula: ##STR19##where x and y are independently selected from integers of from 1 toabout 6, wherein the functionality of said compound is provided by thereaction of at least one of the primary amine groups thereof.